I agree dave. I have almost all the same memberships save the D23 one and feel the same as you do.
In light of trying to have an intellegent discussion about it, why did you choose to purchase into it? What made the $15 extra dollars worth it? Because it didn't sell itself to me.
What made the extra $15 worth it to me?
A vaireity of reasons played into why I joined, and quite frankly I was on the fence for a while. Which means, at least to me, TWDC priced it correctly. $75 is just about my go/no-go point for the membership, any higher and I doubt I would have paid. If I hadn't joined my comment would have been "It's out of my personal range for value vs. cost" Factors that played into me joining.
1) For me, at this point in my life, $75 is not something that is going to make or break me. I don't run out and spend $75 on a item every day of the week, but I if see somthing that is $75 that I want, it's not something that I have to fret over and try and work into my budget.
2) Keeping me out of B&N is an added bonus, If I walk into B&N I come out at least $100 lighter. In addition to the money, I have run out of bookshelf space
3) Charter Memberships appeal to me. Yes it's marketing, yes it's a way to suck people into something. But it is something I enjoy. It's my money, if I enjoy a charter memebership into something then I am wrong for spending my money in a way that brings me enjoyment.
4) I am not a fan of eBay. I am a fan of "If I want to buy something I want to go to a store (or website) and buy it" I may comparison shop for the best price, but I don't enjoy waiting for things to come up on auction, and then decide if its what I really was looking for.
5) I don't do Disney "collections". I don't hang all sorts of stuff on the walls. I don't have shelves with 150 snow globes on them. There are a few Disney articles that are in my house - a throw, a Black Pearl bigfig, cutlery, etc. The merch that is available via D23 appealed to me. I like the design so far, and the sort of understatedness of it.
6) Quite honesty the idea of being a "super fan" never played into it. I figured I would get a magazine delivered to my house, a (hopefully) interesting free gift, some stuff that can go into the "Disney box o' assorted history stuff" and there may be some additional perks down the road.
-dave